Modified Pulsed MOS Capacitor for Characterization of Ultraclean Thin ${rm p}/{rm p}^{+}$ Silicon Epitaxial Layers

摘要

We develop a modified pulsed MOS technique for measuring generation lifetime in ultraclean and thin ${rm p}/{rm p}^{+}$ epitaxial layers, which can be used to detect metallic impurities with densities as low as $10^{10}{rm cm}^{-3}$ . The widely used classic version is shown to be unable to effectively detect such low impurity densities because of the domination of surface generation; whereas, recombination lifetime measurement techniques have serious limitations for layers that have smaller thicknesses than the minority carrier diffusion length.